A fuel cell is an electrochemical device that converts the chemical energy of a reaction into electrical energy. A fuel cell consists of an anode and a cathode separated by an electrolyte layer. In operation, a reactant, typically hydrogen gas, is fed to the anode, and an oxidant, typically air or other oxygen-containing gas, is fed to the cathode. The electrochemical reactions which take place at the fuel cell produce an electric current. Fuel cell power systems generally comprise aggregated series of cells, often called fuel cell “stacks,” to provide higher voltages than are obtainable with a single cell.
Fuel cells have become useful sources of energy in recent years, and there is increasing interest in the use of fuel cells for small-scale and mobile power generation, including vehicular power applications. One impediment to the widespread acceptance of fuel cell power systems is the lack of a broad infrastructure for the production and distribution of fuel, particularly hydrogen, required to operate the fuel cell. Attempts have been made to overcome this problem through the use of hybrid power systems which run on conventional hydrocarbon fuels. In these systems, the hydrocarbon fuels are first converted to hydrogen-containing reformate via an integrated on-board fuel reformer, and the resultant reformate is then used to power the fuel cell.
In the future, it is anticipated that it will become increasingly cost-effective to employ non-hybridized or “pure” hydrogen fuel cell power systems (i.e. with no reformer present), in which the hydrogen is provided by a local hydrogen storage system or (in static applications) directly from a remote source. Also, the use of a separate fuel reformer sub-system can be avoided by feeding the fuel cell with an easily-reformed fuel, such as an alcohol, particularly methanol, so that hydrogen can be formed in situ at the fuel cell anode.
In any of these fuel cell-based power systems, particularly in the case of mobile or portable power generating applications, even modest increases in system efficiency can make a critical difference in terms of size, weight, and cost-effectiveness of the system.